1. Field of the Invention
This invention relates to a wide-angle zoom lens containable in a compact camera, an electronic still camera or the like.
2. Related Background Art
A two-unit type zoom lens of convex-concave construction is known as a conventional zoom lens for a compact camera, and a number of such two-unit type zoom lenses of convex-concave construction have been put into practical use.
As regards the range of the focal length of the conventional two-unit type zoom lens of convex-concave construction, zoom lenses of the order of 35 mm-70 mm as converted into the film size of 35 mm format have been the mainstream.
Also, the zoom lens of this type has few limitations in the back focal length thereof and basically adopts a construction comprising a positive first lens unit G.sub.1 and a negative second lens unit G.sub.2, with the lens in the first lens unit G.sub.1 which is most adjacent to the object side comprised of a positive lens. By such construction, the back focal length is shortened and the compactness of the entire lens is achieved.
However, if an attempt is made to achieve a wide angle of view on the basis of this construction, not only will it become difficult to secure a back focal length great enough to be capable of coping with a compact camera or the like, but also it will become difficult to correct aberrations sufficiently.
For this reason, the focal length of the wide angle end of the conventional two-unit type zoom lens of convex-concave construction has been of the order of 35 mm as described above, and in most cases, this has been 63.4 degrees at greatest when converted into an angle of view.